1. Field of the Invention
This invention relates to steer axle assemblies and, in particular, to draw keys for use in maintaining the position of a steer axle kingpin.
2. Disclosure of Related Art
Conventional steer axle assemblies include an axle beam that defines a boss at either end. Each boss defines a kingpin bore configured to receive a kingpin on which a steering knuckle may be rotatably supported. Each boss further defines at least one additional bore that intersects the kingpin bore. This additional bore is configured to receive a draw key that engages the kingpin and limits movement of the kingpin within the kingpin bore.
In one conventional steer axle assembly, the boss of the axle beam defines two draw key bores that intersect the kingpin bore. One of the draw key bores is disposed on an inboard side of the kingpin bore while the other draw key bore is disposed on an outboard side of the kingpin bore. This conventional steer axle assembly has several disadvantages. First, the beam requires a relatively large amount of material and machining. Second, the kingpin does not have sufficient contact or sufficiently low contact pressures within the kingpin bore to retain the initial assembly fit throughout service life in certain application and design packages. Third, the centerline of the kingpin is angled relative to the centerline of the kingpin bore thereby resulting in additional variation in axle camber. Fourth, the steering knuckle has difficulty clearing the axle boss and outboard draw key and nut during turns. Finally, the axle assembly is difficult to assemble.
There is thus a need for a steer axle assembly that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides a steer axle assembly having an improved draw key arrangement.
A steer axle assembly in accordance with the present invention includes an axle beam that defines a boss at one end. The boss further defines first, second, and third bores. The first bore is disposed about a first axis and the second and third bores both intersect the first bore on an inboard side of the first axis. The assembly further includes a kingpin disposed within the first bore and first and second draw keys disposed within the second and third bores and in engagement with the kingpin. Finally, the inventive assembly includes first and second nuts disposed about the first and second draw keys on one side of the axle beam.
A steer axle assembly in accordance with the present invention has several advantages as compared to conventional steer axle assemblies. The axle beam of the inventive assembly requires less material and may be machined more easily because the draw keys are located on the same side of the kingpin bore. The inboard location of the draw keys also increases the contact area of the kingpin within the kingpin bore and reduces clearance problems during turning of the steering knuckle. Further, the inboard location of the draw keys enables the centerline of the kingpin to align parallel to the centerline of the kingpin bore thereby eliminating one factor influencing axle camber. Finally, the inboard location of the draw keys and the location of the nuts on the same side of the axle beam reduces assembly time as compared to conventional steer axle assemblies.
These and other features and objects of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.